It’s Now Safe To Turn Off Your Computer

By | Saturday 10.12.2016

Remember that old message from older Windows operating systems that said “It’s now safe to turn off your computer.” after you issued the Shut Down command from the Start menu? I just watched a weird video about Windows 95, and I got “triggered” as you kids might say today.

Have you ever wondered what it means? Well, I’m here to give you a little help on that.

You see, when personal computers were created, the first ones were very simple and, unlike the ones today which turn off (and even back on) all by themselves, they had to be manually switched on or off.

This is because they were either using the AT industry standard, or they weren’t even using that at all.

Among other things, during the late 90s a new industry standard appeared that’s been used to this day, called ATX. There exist variations of it, but the base is the same.

One of the new things brought to you by this new motherboard and power supply unit design was the fact that the motherboard itself would be permanently supplied with a small amount of power, in order to allow it to enter low power consumption modes (called sleep states these days), and even power on the whole system if the motherboard supports that function.

This is why you have to physically unplug the computer from the electrical outlet when you’re installing new hardware in it: the motherboard is powered even when the computer is switched off, and connecting electronic components to it might damage it if you do not unplug the computer from the wall socket, and wait about 5 minutes, to ensure all power coming from the power supply unit has dissipated.

One of the things that happened when ATX was implemented was the introduction of a core command to power off the system, and this is why your computer shuts off by itself when you tell it to – but in reality the motherboard and in some cases even the microprocessor – is still supplied with power. This actually damages the motherboard components like capacitors over time, by wearing them out, and it’s no different from keeping your computer running at all times without ever switching it off.

Back to the “safe to turn off” message, don’t worry, nothing bad would happen to your computer if you shut it down any other way. Physically, that is.

The message actually meant that at that point any data which was stored on that computer’s hard drives would be perfectly safe when you shut the power off.

Remember what I’ve said about the ATX standard? Windows 95 sometimes didn’t recognize it (because, as I recall, at the time Windows 95 came out, ATX was only present on certain laptops and very rarely on desktops), so it would always show that message informing you that you can switch off now.

Windows 98 showed that message as well, but only after spinning down all the hard drives (which you could actually hear happening quite clearly if you listened close to the computer case), when it wasn’t possible to turn off power automatically – if your computer was not an ATX.

There was a time when data loss was a great problem with hard drives, and companies even made programs for MS-DOS which you had to manually run to park the hard drive read heads and spin it down before turning your computer off, to ensure that the drive’s heads would not land on a data portion of the internal disc, potentially damaging any data on it (as well as the disc surface itself).

The FAT file system was also the only one viable, and it had problems regarding data integrity if power were to suddenly go out. Ever wondered why in Windows 98 ScanDisk would run automatically if you didn’t use the Shut Down command to turn off the computer? This is why. The same thing is done with disk checking in the latest versions of Windows today.

In conclusion, the famous “It’s now safe to turn off your computer.” message meant that any disk activities have halted and you can safely switch the power off in case the computer can’t do so by itself, and you will not lose any data.

I guess people weren’t so inspired when writing computer messages back then.